Blower noise reducing device and a blower having same

ABSTRACT

A blower noise reducing device for use in a blower having a blower housing defining a volute, a discharge opening through the blower housing, and a discharge nozzle connected over the discharge opening. The blower noise reducing device comprises a moving air deflecting member having a generally triangular cross-section, a first end representing a base of the generally triangular cross-section, a second end representing an apex of the generally triangular cross-section, a first side for mounting against a wall of the discharge nozzle (at a connecting point between the discharge opening and the discharge nozzle), and a second and opposite side for protruding into the discharge opening and discharge nozzle when the first side is mounted against the wall of the discharge nozzle, thereby reducing noise causing characteristics of air being moved by deflecting such moving air in a predetermined manner.

RELATED APPLICATION

[0001] This application is related to U.S. application Ser. No. ______ (Applicants' Docket No. D/A0860Q) entitled “Office Machine Including a Blower Having A Blower Noise Reducing Device” filed on the same date herewith, and having at least one common inventor.

BACKGROUND OF THE INVENTION

[0002] This invention relates to blowers using an impeller assembly to draw in and centrifugally accelerate a air for controlled discharge through a projecting discharge conduit thereof.

[0003] Power blowers, for example those having a tangentially located discharge conduit, are widely used by homeowners, and professionally as stand alone devices, or within a machine or controlled environment for conditioning a air such as air within such environment. Some such power blowers are hand-holdable, gas powered units used for example in landscape and maintenance industries.

[0004] In either case, each such power blower includes a powered drive motor including a drive shaft, and a rotatable impeller assembly coupled to the drive shaft. In such blowers having a tangentially located discharge conduit, the impeller assembly typically has a laterally extending rotational axis, and draws air inwardly as it rotates. Each such blower typically also has an impeller assembly housing including a forwardly and tangentially projecting discharge conduit that can be conveniently oriented for directing air discharge during use.

[0005] In one exemplary construction, the impeller assembly has an unbladed core volume and radially projecting blades having upstream ends at the core volume and downstream ends located radially outwardly therefrom. Operation or rotation of the impeller assembly causes air to be drawn into the core volume, picked up by the blades, centrifugally accelerated in a volute, and diverted at a point of separation from the downstream ends of the blades at high volume into the discharge conduit for directed discharge as described above.

[0006] A significant problem with such powered blowers is that they generate a significant amount of noise during operation. Powered blower designers are therefore constantly seeking ways to further attenuate the noise generated at different locations throughout the powered blower assembly so as to make it more environmentally compatible and acceptable.

[0007] One source or location of noise from such powered blowers has been identified as being at a branching location or juncture where the accelerated flow in the volute divides into a first volume (a) being directed tangentially through the projecting discharge conduit, and a second volume (b) that remains in the volute for recirculation. It has been found that somewhere between these divided flow paths and volumes, some of the air volume is abruptly halted. Such abrupt halting tends to generate significant noise as the impeller assembly blades travel past this location and shear such halted air volume.

[0008] Experimental measurements and calculations therefrom have indicated that such noise in significant part can be attributed to the frequency of the blades passing through the stagnated air at the juncture point. In such experiments, the blade passage frequency is the number of times that an actual blade passes by the juncture or pinch point. As an equation, the blade Passage Frequency=(# of blades) (Rev/Min)(Min/60 Sec)=(6) (2850R/Min)(Min/60 Sec)=285 Pulse/Sec. Tabulation and examination of ⅓ Octive data from the experiment clearly showed that the pure tone fell in an octive band which is relatively close to the 285 Pulse/Sec calculation. This therefore showed that the blade passage frequency was the source of the noise.

SUMMARY OF THE INVENTION

[0009] The invention is directed to a blower noise reducing device for use in a blower having a blower housing defining a volute, a discharge opening through the blower housing, and a discharge nozzle connected over the discharge opening. The blower noise reducing device comprises a moving air deflecting member having a generally triangular cross-section, a first end representing a base of the generally triangular cross-section, a second end representing an apex of the generally triangular cross-section, a first side for mounting against a wall of the discharge nozzle (at a connecting point between the discharge opening and the discharge nozzle), and a second and opposite side for protruding into the discharge opening and discharge nozzle when the first side is mounted against the wall of the discharge nozzle, thereby reducing noise causing characteristics of air being moved by deflecting such moving air in a predetermined manner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a fragmentary, perspective view of an exemplary blower of the present invention including a noise reducing device in accordance with the present invention;

[0011]FIG. 2 is an enlarged, perspective view of the blower in FIG. 1 with part of the housing thereon removed to show the noise reducing device of the present invention;

[0012]FIG. 3 is a schematic of a conventional blower without the noise reducing device of the present invention;

[0013]FIG. 4 is a schematic of the blower of FIG. 2 including the noise reducing device of the present invention;

[0014]FIGS. 5 and 6 are detailed illustrations of the noise reducing device of the present invention; and

[0015]FIG. 7 is a table of noise level measurements from a typical blower without (column 2), and with various models of the noise reducing device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0016] While the present invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

[0017] Referring first to FIGS. 1-2 and 4, a blower in accordance with the present invention, for example, a hand-holdable blower is shown generally as 10. As shown, the blower 10 includes a housing 12 having walls 13, 14 defining an intake region 47, an internal air path or volute 24 through which air moves, and a discharge region 48 including a discharge opening 25. The blower 10 also includes an air moving assembly in the form of a bladed impeller assembly 16, which rotates around a laterally extending axis 18 to draw air axially inwardly, as indicated by the arrow 20, through a grill 22 within the intake region 47. The impeller assembly 16 then directs the incoming air radially and outwardly into the volute 24. Within the volute 24, the air is centrifugally accelerated by the impeller assembly blades 36, towards the discharge region 48, and ultimately communicated to and through the discharge opening 25 into a discharge conduit 26. The impeller assembly 16 for example can be rotated by any suitable power device such as a gas or electric powered motor 28 which is regulated by controls 30, which in the case of a hand-holdable blower, can be located on a handle 32.

[0018] The precise air flow pattern into and through the blower housing 12 can be seen for example in FIGS. 3 (prior art) and 4. In each case, the motor 28 drives the impeller assembly 16 in the direction of the arrow 34. The impeller assembly 16 has radially projecting blades 36 which are spaced uniformly around the axis 18 of the impeller assembly 16. Relative to air movement, each blade has an upstream end 38 and a radially outwardly spaced downstream end 40. Between the axis 18 and the upstream ends 38 of the blades 36, a core volume 42 exists that does not have any air accelerating blades therewithin.

[0019] The blades 36 when being rotated, centrifugally propel air against a radially and inwardly facing surface 44 of the volute 24. As such, a low pressure region is thereby developed in the core volume 42, as a result of which intake air is drawn axially and laterally through the air intake grill 22 and into the core volume 42. Initially, the air flows axially, then the impeller assembly 16 abruptly changes its direction is so that it then flows in the radial direction as described above. The radial flow again abruptly changes direction upon encountering the radially and inwardly facing surface 44 of volute 24, after which such air then moves in a curved path, through the volute 24, in the direction of the arrow 34.

[0020] The volute 24 may be designed such that it progressively increases in volume from the intake region 47 towards the discharge region 48. As illustrated, within the volute 24, the air is moved from the intake region 47, and is accelerated and expanded, in the progressively increasing volume of the volute 24, until some of it, after branching at a juncture or pinch point 50, is discharged through the discharge opening 25 into the discharge conduit 26. The rest of it, after branching at a juncture or pinch point 50, continues to move through the volute 24.

[0021] Typically, a blower 10, 11 has a number of areas at which noise generation is significant when moving air as above through the volute 24. For example, as shown in FIG. 3 (prior art), an area of significant noise generation is located at the branching juncture or pinch point 50 where the air accelerated by the impeller assembly 16 branches so that some of it is discharged through the discharge opening 25 and into the discharge conduit 26, and the rest re-enters the volute 24 at the intake region 47.

[0022] As illustrated, the juncture or pinch point 50 is located at an intersection of a first generally flat surface 52 of the walls 13, 14 of blower housing 12, and a second generally flat surface 54 of the wall 27 of the discharge conduit 26. Because the discharge nozzle 26 is arranged for tangential flow of accelerated air out of the volute 24, the juncture or pinch point 50 as shown in FIG. 3 is ordinarily at a V-shaped apex 56 defined by the flat surface 52 of the blower housing 12 and that 54 of the nozzle wall 27, meeting and being connected in an impervious manner.

[0023] It has been found that at the juncture or pinch point 50 between the surfaces 52, 54 there is ordinarily a stagnation point 58 within the volute 24, and a stagnation point 59 within the discharge nozzle 26 (FIG. 3), where some of the air being accelerated and branched between the continued volute 24 and the discharge conduit 26, abruptly stops and is stagnated. Such stagnated air within the volute 24 is then sheared by the radially outwardly spaced downstream end 40 of each of the rotating blades 36 as it is rotated passed the juncture or pinch point 50. The shearing has been found to cause and produce a significant amount of noise, for example, see TABLE 1 and FIG. 7, column 2 in each case.

[0024] Referring now to FIGS. 4-6, it has been found that the shearing noise caused at the juncture or pinch point between the flat surface of a volute and a flat surface of a discharge conduit in a blower (for example juncture or pinch point 50) can be significantly reduced by a blower noise reducing device 60. As shown, the blower noise reducing device 60 can be formed as a part of the housing 12 or discharge conduit 26. It can also be an insert that is attached to either or both the housing 12 or conduit 26, and over what would ordinarily be the apex 56 at the juncture or pinch point, for example juncture or pinch point 50. As further illustrated, the noise reducing device 60 comprises a moving air deflecting member 62 that has a generally triangular cross-section 64, a first end 66 representing a base 67 of the generally triangular cross-section, a second end 68 representing an apex portion 70 of the generally triangular cross-section 64, a first side 72 for mounting against a wall of the discharge nozzle 26 (at the connecting point and hence at the juncture or pinch point 50 between the discharge opening 25 and the discharge nozzle 26) and a second and opposite side 74. The second and opposite side 74 as shown is shaped for protruding into the discharge opening 25 and into the discharge nozzle 26 when the first side 72 is formed or mounted against the wall 27 of the discharge nozzle 26. It has been found that the noise reducing device 60 as shaped, and when formed or mounted as described, significantly alters the noise causing characteristics (for example stagnation) of some of the air being moved within the volute 24, ass well as within the discharge nozzle 26. The noise reducing device 60 does so by aerodynamically deflecting such moving air in a predetermined manner as shown in FIG. 4.

[0025] As further shown, the moving air deflecting member 62 includes a heel-like or heel portion 76 located at the first end 66 for projecting into the volute 24, particularly into the intake region 47 of the volute for modifying the inside profile of the volute, and hence the flow pattern of the air being moved, at the discharge opening 25, in other words at the intake region 47. The heel portion 76 has a first surface 77 aligned with the base 67 of the triangular cross-section 64, and a second surface 78 for attaching to, or that is connected to, the inside of the walls 13, 14 of the volute 24. The second surface 78 of the heel portion 76 comprise the part thereof projecting into the volute 24. The projection of the heel portion 76 into the volute 24 of course is such as not to interfere with free movement or rotation of the distal ends 40 of the rotating blades 36 of the blower impeller assembly 16. The projection or protrusion of the second surface 78 of the heel portion 76 into the volute 24 changes or alters the profile of the blower volute tongue or intake region 47. The projection or protozoon of the second side 74 into the discharge nozzle 26 also changes or alters the profile of the discharge nozzle 26 near the juncture 50.

[0026] These changes or alterations have been found to minimize air stagnation, and hence air shear at or near the juncture 50. The result is a significant reduction in the overall noise level, as well as in the blade passage noise level. As shown in FIG. 7, in one experiment, such noise for example was reduced significantly from 78.1 dB to 71 dB in the 500 Octive bandwidth.

[0027] In the case where the air deflecting member 62 or noise reducing device 60 is an insert, the heel portion 76 may include provisions or features 80 for allowing or enabling it to be attached to the walls 13, 14 and 27 of the volute 24 and nozzle 26, respectively.

[0028] As mounted, that portion of the noise reducing device 60 or the moving air deflecting member 62 that lies within the discharge nozzle 26, comprises a reverse-aerofoil in shape, relative to air being discharged by the blower through the nozzle 26. As a consequence, the discharge nozzle 26 becomes more aerodynamic and efficient and thus also contributing to the reduction in overall noise level.

[0029] When the noise reducing device 60 is an insert, it need not be made of the same material as the walls 13, 14 of the blower housing. In fact, it can be made of a suitable non-metallic material such as rubber, plastic, or wood, or out of a suitable metallic material, provide any such material is an air impervious material so as to suitably deflect moving air. The insert as such can then be installed or retro-fitted into even off-the-shelf blowers for reducing blower noise, and without affecting performance of the blower. Where the attaching or mounting provision is for example an adhesive, or merely a friction fitting slot over the V-shaped apex 56 of the blower housing, the insert or moving air deflecting member 62 can therefore be easily added or retro-fitted to an existing standard blower with no tooling costs to the blower supplier.

[0030] Without the present invention, the typical conventional approach for noise reducing blower noise would be to add a muffler system which is more costly and would complicate the overall air system. The benefits from use of the noise reducing device 60 of the present invention therefore include the reduced noise level itself, and the avoidance or replacement of such muffler systems.

[0031] Table 1, and FIG. 7 illustrate the effectiveness of the present invention by showing experimental measurements of blower noise at various Octive Bands (column 1) for a typical blower without the present invention (column 2), and for reductions due to use of trial models of the device of the present invention to modify the tonge/pinch point of the particular blower.

[0032] In this experiment, the blade passage frequently is the number of times that an actual blade passes by the pinch point. As an equation:

Blade Passage Frequency=(# of blades) (Rev/Min)(Min/60 Sec)=(6) (2850R/Min)(Min/60 Sec)=285 Pulse/Sec.

[0033] A look at the ⅓ Octive data clearly shows that the pure tone falls in the 312 octive band which is relatively close to the 285 Pulse/Sec calculation. This therefore shows that the blade passage frequency is the source of the noise. TABLE 1 ⅓ Blower Blower Blower Blower Blower Reduc- Octive Without With With With With tion Bands invention Mod. 1 Mod. 4 Mod. 11 Mod. 12 dB 160 63 db 63 63 64 63 0 200 73.4 72.1 71 71 69 −4.4 250 73.1 72 71 69 69 −4.1 315 82.2 79 78 77 77 −5.2 400 78.2 75 74 74 73 −5.2 500 78.1 76 74.1 74 71 −7.1

[0034] As can be seen, there has been provided a blower noise reducing device for use in a blower having a blower housing defining a volute, a discharge opening through the blower housing, and a discharge nozzle connected over the discharge opening. The blower noise reducing device comprises a moving air deflecting member having a generally triangular cross-section, a first end representing a base of the generally triangular cross-section, a second end representing an apex of the generally triangular cross-section, a first side for mounting against a wall of the discharge nozzle (at a connecting point between the discharge opening and the discharge nozzle), and a second and opposite side for protruding into the discharge opening and discharge nozzle when the first side is mounted against the wall of the discharge nozzle, thereby reducing noise causing characteristics of air being moved by deflecting such moving air in a predetermined manner. 

What is claimed is:
 1. A blower noise reducing device for use in a blower having a blower housing defining a volute, a discharge opening through the blower housing, and a discharge nozzle connected over the discharge opening, the blower noise reducing device comprising a moving air deflecting member having: a. a generally triangular cross-section; b. a first end representing a base of said generally triangular cross-section; c. a second end representing an apex of said generally triangular cross-section; d. a first side for mounting against a wall of the discharge nozzle (at a connecting point between the discharge opening and the discharge nozzle); and e. a second and opposite side, said second and opposite protruding into the discharge opening and discharge nozzle when said first side is mounted against the wall of the discharge nozzle for reducing noise causing characteristics of air being moved by the blower by deflecting such moving air in a predetermined manner.
 2. The blower noise reducing device of claim 1, wherein said moving air deflecting member includes a heel portion at said first end.
 3. The blower noise reducing device of claim 1 wherein said first end representing said base of said generally triangular cross-section has an external surface for projecting into the volute.
 4. The blower noise reducing device of claim 1, wherein as mounted within the discharge nozzle, said moving air deflecting member comprises a reverse-aerofoil relative to air being discharged through the discharge nozzle.
 5. The blower noise reducing device of claim 1, wherein said moving air deflecting member is made of a non-metallic material.
 6. The blower noise reducing device of claim 1, wherein said moving air deflecting member is made of a metallic material.
 7. The blower noise reducing device of claim 2, wherein said heel portion has a first surface aligned with said base of said triangular cross-section.,
 8. The blower noise reducing device of claim 2, wherein said heel portion has a second surface for attaching to a wall of the volute.
 9. An air blower comprising: (a) a housing having walls defining an intake region for incoming air, a discharge region including a discharge opening for discharging air from said housing, and an air path for controllably directing air entering said intake region towards said discharge region; (b) an air moving assembly including a rotatable impeller assembly mounted within said housing for drawing air into said air path through said intake region, and for accelerating air within said air path towards said discharge region; (c) a discharge nozzle, mounted over said discharge opening, for directing air being discharged away from said housing; and (d) a blower noise reducing device comprising a moving air deflecting member having: (i) a generally triangular cross-section; (ii) a first end representing a base of said generally triangular cross-section; (iii) a second end representing an apex of said generally triangular cross-section; (iv) a first side for mounting against a wall of the discharge nozzle (at a connecting point between the discharge opening and the discharge nozzle); and (v) a second and opposite side, said second and opposite protruding into the discharge opening and discharge nozzle when said first side is mounted against the wall of the discharge nozzle for reducing noise causing characteristics of air by deflecting such moving air in a predetermined manner.
 10. The air blower of claim 9, wherein said moving air deflecting member includes a heel portion at said first end.
 11. The air blower of claim 9 wherein said first end representing said base of said generally triangular cross-section has an external surface for projecting into the volute.
 12. The air blower of claim 9, wherein as mounted within the discharge nozzle, said moving air deflecting member comprises a reverse-aerofoil relative to air being discharged through the discharge nozzle.
 13. The air blower of claim 9, wherein said moving air deflecting member is made of a non-metallic material.
 14. The air blower of claim 9, wherein said moving air deflecting member is made of a metallic material.
 15. The air blower of claim 9, wherein said discharge nozzle is attached tangentially to said blower housing.
 16. The air blower of claim 9, wherein said air moving assembly includes drive means for rotating said impeller assembly.
 17. The air blower of claim 9, wherein a volume of said air path increases from said intake region to said discharge region.
 18. The air blower of claim 10, wherein said heel portion has a first surface aligned with said base of said triangular cross-section.,
 19. The air blower of claim 10, wherein said heel portion has a second surface for attaching to a wall of the volute.
 20. An air blower comprising: (a) a housing having a housing wall defining an air path, and an air discharge opening; (b) a discharge nozzle, mounted over said discharge opening for directing air being discharged away from said housing; (c) a pinch point formed between said housing wall and said discharge nozzle at said discharge opening; (d) an air moving assembly including a rotatable impeller assembly mounted within said housing for drawing air into said air path; and (e) a blower noise reducing device on said pinch point for minimizing air stagnation at said pinch point, said blower noise reducing device including a first surface for protruding into said air path, and a second surface for protruding into said discharge nozzle for minimizing air stagnation within said air path and within said discharge nozzle. 